Registered

I have a 2012 with egr and emissions delete, mini max tuner.
4x4 cc LB
The original turbo went out about 8 months ago.
I replaced with a 2015 upgrade kit from midwest diesel and opted for the streetmax turbine for increased reliability.
I have noticed that there was significant turbo bark (there seems to be some degree of confusion in the diesel world as to what TRUE turbo bark is) at the shifting points between 3 to 4, 4 to 5, and 5 to 6.
More specifically, the turbo barks are associated with boost pressures above about 9 or 10. If I set the transmission in M mode and manually shift earlier, turbo bark is very minimal.
It's also worse with cold weather (makes sense because cold air has greater density).
I tried to attach a video for reference, but it was to large, even in zip format.

Premium Member

If it's anything like the "turbo fart" (6.0L) that people reference it's due to the compressor. The sound is compressor stall, when the drive pressure is suddenly taken off a turbo, the compressed air in the rest of the system tries to escape through the compressor. Throttle off, the VGT vanes open, drive pressure is gone, so the air pushes back.

Vendor

The bark is called compressor surge. it happens to all turbos, but you get to hear it more with an open element filter. Torque reduction from the computer during shifts exacerbates the issue. The bark comes from shutting off the exhaust energy to the turbine. When that happens, the shaft speed slows down abruptly. Then all the compressed air in the intake tract tries to back flow thru the compressor. When you've got your foot in the throttle and the engine is at higher rpm and making more torque, the shifts don't have the same effect. The engine can make enough exhaust energy to keep the turbo spooled up.

That said, is a single turbo an upgrade? Maybe, maybe not. I like the Dual Axial Compressor system. I'd like it to be a little bigger, but it does a really good job. Making more power requires more air. So it does have it's limitations. But I think drivability is much better than with the standard style turbos.